On Wed, Apr 13, 2016 at 05:09:54PM +0800, Fam Zheng wrote:
> Because virtlockd in libvirt already uses the fcntl lock on the image file, we
> have to workaround this by locking a digest-mapped temporary file.
>
> Signed-off-by: Fam Zheng <f...@redhat.com>
> ---
> block/raw-posix.c | 97
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 97 insertions(+)
>
> diff --git a/block/raw-posix.c b/block/raw-posix.c
> index 906d5c9..277f20d 100644
> --- a/block/raw-posix.c
> +++ b/block/raw-posix.c
> @@ -35,6 +35,7 @@
> #include "raw-aio.h"
> #include "qapi/util.h"
> #include "qapi/qmp/qstring.h"
> +#include "glib.h"
>
> #if defined(__APPLE__) && (__MACH__)
> #include <paths.h>
> @@ -149,6 +150,9 @@ typedef struct BDRVRawState {
> bool discard_zeroes:1;
> bool has_fallocate;
> bool needs_alignment;
> + bool image_locked;
> + int lock_file_fd;
> + char *lock_file_name;
> } BDRVRawState;
>
> typedef struct BDRVRawReopenState {
> @@ -397,6 +401,87 @@ static void raw_attach_aio_context(BlockDriverState *bs,
> #endif
> }
>
> +static int raw_do_lockf(int fd, BdrvLockfCmd cmd)
> +{
> + int ret;
> + struct flock fl = (struct flock) {
> + .l_start = 0,
> + .l_whence = SEEK_SET,
> + .l_len = 0,
> + };
If you change this to
.l_start = 1,
.l_len = 1,
then you would be telling a selective lock at byte 1 which would
not interfere with anything virtlockd currently does, and also
leave the other bytes unlocked for future use by QEMU or libvirt
as needed.
Regards,
Daniel
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